1. Field of the Invention
The present invention relates to an apparatus and a method for analyzing a specimen by means of X-rays.
2. Description of the Related Art
A known X-ray analysis apparatus is described in Japanese Patent Application Laid-Open Publication No. 2000-146871. The known X-ray analysis apparatus is adapted to irradiate a micro-specimen or a micro-part of a specimen with a parallel X-ray beam and detect X-rays diffracted by the micro-specimen or the like by means of a two-dimensional X-ray detector. With the known X-ray analysis apparatus, it is possible to evaluate the grain size and the preferred orientation of the specimen and identify single crystal, strongly oriented polycrystal and amorphism by directly observing a Debye ring by means of the two-dimensional X-ray detector. Additionally, it is possible for the X-ray analysis apparatus to perform various measuring operations that are not allowed to a zero-dimensional X-ray detector such as SC (scintillation counter) or a one-dimensional X-ray detector such as PSPC (position sensitive proportional counter).
In addition to above-described measurement using a parallel X-ray beam, X-ray measurement using a optical system for the focusing method is also known. The focusing method is achieved by using a light diverging slit for causing a divergent beam to strike a specimen, a light receiving slit arranged on a spot region on the focusing circle (also referred to as the Rowland circle) where X-rays diffracted by the specimen are converged and a zero-dimensional X-ray detector arranged behind the light receiving slit as disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 9-229879. With the focusing method, the specimen is driven to rotate around an axial line that runs through the specimen itself, a so-called θ axial line, in order to measure the angle of diffraction 2θ. This rotation is referred to as θ rotation of the specimen.
An X-ray analysis apparatus realized on the basis of the focusing method has an advantage that it provides an excellent resolution and the intensity of the diffracted X-rays is very strong as compared with the above-described parallel beam method. Because of this advantage, the focusing method is being widely used to observe a relatively large specimen such as a powdery specimen covering an area of about 20 mm×10 mm. As pointed out above, X-ray measurement using a two-dimensional X-ray detector and a parallel X-ray beam and X-ray measurement using an optical system for the focusing method have respective advantages and conventionally they are used selectively depending on the situation. However, there arises a problem that two measurement systems need to be held ready at high cost so long as these two modes of measurement are employed selectively. Additionally, there is also a problem that measuring operations selectively using these two modes of measurement are very cumbersome and inconvenient.
Facing of these problems, the inventor of the present invention came to believe that an X-ray measuring operation based on the parallel beam method and an X-ray measuring operation based on the focusing method can be selectively conducted with ease if an optical system for the focusing method can be used for a two-dimensional X-ray detector. However, such a selective use is extremely difficult because of the reason as pointed out below.
When only an optical system for the focusing method is arranged in front of a two-dimensional X-ray detector and the specimen is simply subjected to the θ rotation for measurement on the basis of the focusing method, the two-dimensional X-ray detector picks up not only diffraction intensity data that needs to be obtained but also unnecessary X-rays and hence it is far from possible to obtain practically feasible data with a low S/N ratio.